1. Field of the Invention
The present invention relates to defect detection in semiconductor materials. More specifically, the invention concerns a new X-ray Diffraction (XRD) method to acquire XY mapping of the distribution of single crystals, poly-crystals, and twin defects across an entire semiconductor wafer. A reference journal paper by inventors is available at Journal of Crystal Growth, 310 (2008) p. 2724-2731.
2. Description of the Related Art
The disclosure of our commonly filed patent application entitled “Rhombohedral Cubic Semiconductor materials On Trigonal Substrate With Single Crystal Properties and Devices Based on Such Materials,” Ser. No. 12/288,379(the “Rhombohedral Cubic Semiconductor Disclosure”), as well as that of other commonly-filed applications, which as stated above have been incorporated into this disclosure by reference, discusses the phenomenon of “twin defects.” As explained in those disclosures, when a cubic material layer, such as a layer comprised of group IV, group or group II-VI materials, or alloys thereof, is grown on the (0001) c-plane of a trigonal or hexagonal crystal substrate, the epitaxial layer often contains primary twin defects that are 60° rotated on the (111) plane. The atomic alignment of the cubic crystalline allows poly-type crystalline structures with such 60 degree-rotated twin defects as a result of stacking faults as well as twinning on the interface with the underlying trigonal or hexagonal substrate.
It is desirable to be able to map the distribution of single crystalline material and twin defect material on the wafer, in order to control the quality of epitaxial layers for device fabrication on the wafer. Preferably, the method for such mapping should be nondestructive and should be capable of mapping defects across the entire wafer.
Previously, twin defects were measured with electron microscopy so that only a very small region was characterized. Characterization over entire wafer was not possible with that method. The disclosure of commonly-filed application entitled “Method of Generating X-Ray Diffraction Data for Integral Detection of Twin Defects in Super-Hetero-Epitaxial Materials,” Ser. No. 12/254,150, (the “Companion XRD Disclosure”), which as stated above has also been incorporated herein by reference, contains an integral XRD characterization method to measure an averaged property of an entire wafer. However, it does not have a spatial resolution to obtain a wafer mapping with an XY scan.
Accordingly, despite advances in the field, there remains a need for a nondestructive analytic method for defect characterization in two dimensions across wafers of rhombohedral super-hetero-epitaxial materials.